Herbicide spray drift is the movement of herbicides from the target area to areas where herbicide application was not intended. Herbicide spray drift may injure susceptible crops and could cause prohibited residues in the harvested crops. Drift can cause non-uniform application in a field with possible crop damage and/or poor weed control. Drift can also cause surface water contamination and health risks for animals and people. Spray drift can be reduced by increasing droplet size of the spray, as wind moves larger droplets less than smaller droplets.
Hard water, when used as a carrier for spray solutions, can adversely affect the effectiveness of certain salt-formulated herbicides such as glyphosate, sethoxydim, imazethapyr, glufosinate, 2,4-D amine salt and dicamba. Natural waters usually contain ions of calcium (Ca+2), magnesium (Mg+2), and iron (Fe+3). Hard water ions can bind with salts of certain herbicides and with some surfactants to form insoluble salts and reduce the effectiveness of herbicides and surfactants.
Adding agents such as ammonium sulfate (AMS), has been shown to increase herbicide efficacy on a broad spectrum of weed species under hard water conditions. U.S. Pat. No. 4,681,617 to Ghyczy et al. entitled “Phospholipid Compositions and their Use in Plant Protection Spray Mixtures” discloses the use of phospholipids as drift reduction agents.
U.S. Pat. No. 6,797,673 to Worthley et al. entitled “Lecithin-Containing Drift Control Composition for Use in Spraying Agricultural Acreage” discloses the use of lecithin as drift reduction agent in a composition comprising a methyl ester and a non-ionic surfactant.